1. Field of the Invention
The present invention relates generally to imaging arrays, and more particularly, to a photodetector that can operate at room temperature, with first stage amplification, and which will minimize dark current generation and capacitance per unit optical area.
2. Background Information
In solid state photodetectors, photons are converted to electrons and the electron signal is subsequently amplified for further use. Current state of the art amplifying electronics require that the photodetector provide first stage amplification in order to overcome downstream amplifier noise in high bandwidth systems. Avalanche photodiodes (APDs) can provide first stage amplification gain. However, the signal to noise ratio in present APDs is too small. Current ADPs suffer from too much dark current generation and too much capacitance per unit optical area to be used in room temperature photon counting imagers. Both dark current and APD capacitance contribute to the overall noise floor of the photodiode.
Photon counting imaging arrays using P—I—N photodiodes without amplification operate with relatively long integration times. This operation places a premium on minimizing detector dark current. It is anticipated that the total dark current per pixel will need to be <0.2 fA at room temperature in order to meet noise requirements.
Present SWIR P—I—N photodiodes have been demonstrated with dark currents that are roughly six orders of magnitude higher than this requirement. Thus, minimizing the dark current and photodiode capacitance is necessary to reach levels that will result in single photon counting.
Therefore, it would be desirable to provide a photodiode that overcomes the above problems. The photodiode must be able to minimize both the dark current and the capacitance in order to reduce overall noise.